1. Field of the Invention
The present invention relates to a drive circuit device for a power semiconductor and to a signal transfer circuit device for use therein. More particularly, the present invention relates to what drives a so-called power semiconductor, such as a silicon-carbide (SiC) semiconductor element, an insulated gate-type bipolar transistor (IGBT), a MOSFET, and the like, that is used as a main circuit of a hybrid automobile, an electric-powered vehicle, an inverter, a servo control device, and the like.
2. Description of Related Art
FIG. 10 shows a conventional power semiconductor drive circuit device for driving a motor mounted in a hybrid automobile, etc. and a signal transfer circuit device for use therein. A power semiconductor drive circuit device 30A is provided with: an electronic control device 32; a signal transfer circuit device 300A; a power semiconductor 40; and a motor 50. The electronic control device 32 generates a control input signal for controlling the motor 50 mounted, for example, in a hybrid automobile via the power semiconductor 40. The signal transfer circuit device 300A is provided with: a transmission pulse generator circuit 320; a signal transfer circuit 330A; and a receiver circuit 340A. In the signal transfer circuit 330A, a photocoupler or a transformer is used for galvanically isolating a transmitter side and a receiver side of the signal transfer circuit device 300A.
FIG. 11 shows a signal transfer circuit device disclosed in FIG. 1 of JP-A-(H)9-8624 (hereinafter, referred to as Patent Document 1). The signal transfer circuit device disclosed therein is provided with: a transmitter circuitry portion 11; a receiver circuit portion 12; and a signal transfer circuit 17. The transmitter circuitry portion 11 is provided with: a signal generator circuit 13; a rising edge detector circuit 14; and a falling edge detector circuit 15. The receiver circuitry portion 12 is provided with a signal processing circuit 16. The signal transfer circuit 17 transmits a transfer signal generated by the transmitter circuitry portion 11 to the receiver circuitry portion 12, and is used as an isolator for both the circuitry portions. For the signal transfer circuit 17, one or two pulse transformers are used.
Patent Document 1 has a feature that in the isolator, namely the signal transfer circuit 17, a pulse transformer is used instead of a photocoupler. This leads to a reduced shift in timing for transferring signals, and hence to a further reduced power consumption.
FIG. 12 shows an isolator disclosed in FIG. 1 of U.S. Pat. No. 7,075,329 (hereinafter, referred to as Patent Document 2); an isolator 100 is provided with: a glitch filter 101; edge detectors 102 and 104; an inverter 106; transformers 108 and 120; and a flip-flop 110. The transformer 108 is formed with a primary winding 108A and a secondary winding 108B. The transformer 120 is formed with a primary winding 120A and a secondary winding 120B. The primary windings 108A and 120A, and the secondary windings 108B and 120B are connected to a ground potential A (GND A), and to a ground potential B (GND B) galvanically isolated from the ground potential A, respectively.
Moreover, with reference to FIG. 8 of Patent Document 2, a transmitter circuit 802, a top coil 806A that functions as the primary winding, the ground potential A (GND A), and the like are provided on a side of a first substrate 804; on the other hand, a receiver circuit 810, a bottom coil 806B that functions as the secondary winding, the ground potential B (GND B), and the like are provided on a side of a second substrate 808. Patent Document 2 suggests a technical idea that an isolator is so formed as to include a transformer on an IC chip.
However, what is done by the power semiconductor drive circuit device shown in FIG. 10 is to transmit, in a one-way only, a control input signal Sin generated by the electronic control device 32 to a side where the power semiconductor 40 and the motor 50 are present. Therefore, the power semiconductor drive circuit device 30A is not equipped with any means for, in an event of a malfunction occurring to the device, detecting, solving, and obviating the malfunction.
Moreover, Patent Document 1 teaches basic circuit operations assigned to the signal transfer circuit device using a pulse transformer, but fails to suggest any solutions for coping with a delay in transferring the signals and for coping with erroneous operations owing to noise. In a case where the isolator taught by the Patent Document 2 is formed on an IC chip, typically primary and secondary windings of a transformer form a multilayer by being wired with an insulating film in between on one chip. With this configuration, the insulating film lies between a top coil (a primary or a secondary winding) and a bottom coil (a secondary or a primary winding) formed on the IC chip, possibly leading to unwanted mutual interference and hence degraded electrical characteristics. Such problems may prevent a signal on a transmitter side from being transferred to a receiver side in a faithful form, thus making the signal transfer circuit fail to maximize a function inherent thereto.